As the cover stock of two-piece golf balls and wound golf balls, ionomer resins which are metal ion crosslinked forms of ethylene/unsaturated carboxylic acid copolymers have been widely used and accepted because of their restitution, long-lasting impact resistance and cut resistance. Since the ionomer resins provide hard hitting feel and high hardness as compared with the balata rubber conventionally used as the cover stock, ionomer covered golf balls are said difficult to impart a desired spin rate on iron shots and hence, difficult to control.
As a solution to such problems, Sullivan, U.S. Pat. No. 4,884,814 or JP-A 308577/1989 discloses to blend a soft ionomer resin that is a metal ion crosslinked form of an ethylene/unsaturated carboxylic acid/unsaturated carboxylate terpolymer with a metal ion crosslinked form of an ethylene/unsaturated carboxylic acid copolymer. There is obtained a golf ball which is improved in hardness, hitting feel and control.
The metal ion crosslinked form of an ethylene/unsaturated carboxylic acid/unsaturated carboxylate terpolymer, however, is less resilient. Using its blend with a metal ion crosslinked form of an ethylene/unsaturated carboxylic acid copolymer as a cover stock is not effective for adding to the distance of a golf ball.